Search for oxides showing visible-light active photochromism and visible-induced structural change by Raman Spectroscopy.

本研究的目的是寻找在安全、廉价的可见光照射下发生结构变化或光致变色的氧化物，并阐明这种现象的机理。阐明了Y基高Tc超导体YBa_2Cu_3O_x在可见光照射下发生结构变化，并且氧化钒V_2O_3表现出可见光光致变色。1. YBa_2Cu_3aO_（3-x）的光致结构变化和光开关过程阐明了在波长为515 nm的绿色激光照射下，测量YBa_2Cu_3O_x单晶的拉曼谱时，对应于CuO链的缺陷诱导模的强度随时间而减弱，并向亚稳态转移。在波长为900 nm的激光照射下，该状态恢复到原始状态。事实证明，光诱导的结构变化可以通过使用两种不同的光可逆地发生，并且可以用作光开关。氧化钒可见光致变色可逆性的评价在空气中，多晶V_2O_5在可见光（515 nm）照射下，由于V^<5+>的光还原而变成蓝黑色，在400℃加热时，着色减弱，着色-脱色循环可重复。为了评价V_2O_5可见光致变色的可逆性。测量光致发光（PL）光谱。在不照射的情况下重复照射和加热样品。PL强度在加热后的休息期间恢复，并在照射期间一致地衰减。可以重复该循环而不显著降低光致变色效应。

The purpose of this study is to search for oxides showing structural changes or photochromisms under illumination of safe and cheap visible lights and to elucidate mechanisms of the phenomena. It was elucidated that the Y-based high-tc superconductor YBa_2Cu_3O_x underwent change in its structure upon visible-light illumination and that vanadium oxide V2Os exhibited visible-light photochromism-In this year, the light-switching process and the reversibility of these materials have been inestigated in details1.Light-induced structural change and light-switching process in YBa_2Cu_3aO_xIt was elucidated that when Raman spectra of YBa_2Cu_3O_x single crystals were measured under illumination of green laser with a wave length of 515nm, the intensities for defect-induced modes corresponding to CuO chains decreased with time and it was transfered to a metastable state. This state was recovered to the original state upon the illumination of a laser with a wavelength of 900nm. It has turned out that the light-induced structural change can occur reversibly by use of two different lights and it can be used as a light switch.2. Evaluation of the reversibility of visible-Light photochromism in vanadium oxidePolycrystalline V_2O_5 turns blue-black upon irradiation with visible laser light (515nm) in air due to photo reduction of V^<5+> The coloration was diminished when heated at 400℃, and the coloration-decoloration cycle was repeatable. In order to evaluate the reversibility of the visible-light photochromism in V_2O_5. photo luminescence (PL) spectra were measured. The sample was repeatedly irradiated and heated without irradiation. The PL intensity recovers during the rest upon heating and decays consistently during irradiation. This cycle can be repeated without significant degradation of the photochromic effect.